Ben Nelson won't seek re-election in '12

First Read has confirmed, per a high-ranking Democratic source, that Nebraska Sen. Ben Nelson (D) will NOT seek re-election in 2012.

Due to some tough polling numbers for Nelson, Democrats already had a pretty good chance of losing this seat next year. But Nelson's decision not to seek re-election makes it harder to keep the seat in the red state of Nebraska.

*** UPDATE *** That is, if the Democrats can't find a top-notch recruit. The same high-ranking Democratic source tells NBC News that former Nebraska Sen. Bob Kerrey (D) is considering a run with Nelson's seat open.

And the source sends this shot at the conservative Nelson, who often voted with Republicans: "He will be the least missed member of the Democratic caucus next year."

Facing a tough re-election next year, Nebraska Senator Ben Nelson has announced that he will retire at the end of his current term. NBC's Mark Murray dicsusses how this could affect the balance of power in the Senate.